"I remember now that Led Zep's theivery is well known; courtesy of Wilson & Allroy, here are some more famous lifts:
'Babe I'm Gonna Leave You' - A folk song by Anne Bredon, this was originally credited as 'traditional, arranged by Jimmy Page,' then 'words and music by Jimmy Page,' and then, following legal action, 'Bredon/Page/Plant.'
'Black Mountain Side' - uncredited version of a traditional folk tune previously recorded by Bert Jansch.
'Bring It On Home' - the first section is an uncredited cover of the Willie Dixon tune (as performed by the imposter Sonny Boy Williamson).
'Communication Breakdown' - apparently derived from Eddie Cochran's 'Nervous Breakdown.'
'Custard Pie' - uncredited cover of Bukka White's 'Shake 'Em On Down,' with lyrics from Sleepy John Estes's 'Drop Down Daddy.'
'Dazed And Confused' - uncredited cover of the Jake Holmes song (see The Above Ground Sound Of Jake Holmes).
'Hats Off To (Roy) Harper' - uncredited version of Bukka White's 'Shake 'Em On Down.'
'How Many More Times' - Part one is an uncredited cover of the Howlin' Wolf song (available on numerous compilations). Part two is an uncredited cover of Albert King's 'The Hunter.'
'In My Time Of Dying' - uncredited cover of the traditional song (as heard on Bob Dylan's debut).
'The Lemon Song' - uncredited cover of Howlin' Wolf's 'Killing Floor' - Wolf's publisher sued Zeppelin in the early 70's and settled out of court.
'Moby Dick' - written and first recorded by Sleepy John Estes under the title 'The Girl I Love,' and later covered by Bobby Parker.
Nobody's Fault But Mine" - uncredited cover of the Blind Willie Johnson blues.
"Since I've Been Lovin' You" - lyrics are the same as Moby Grape's "Never," though the music isn't similar.
"White Summer" - uncredited cover of Davey Graham's "She Moved Through The Fair."
"Whole Lotta Love" - lyrics are from the Willie Dixon blues "You Need Love."